Fuse



00529; 1940. s. JONES 2219,705

FUSE

Filed Jan. 11, 1939 570 0920 Jone$ Patented Oct. 29, 1940 UNITED STATES PATENT OFFICE FUSE Application January 11, 1939, Serial No. 250,424

5 Claims.

My invention relates to grounded electric fuses of the type intended to afford protection against lightning and other high voltages and excessive currents, it being intended particularly for use for the protection of domestic appliances though not limited to such use.

It is an object of the invention to provide a device of this character which shall be of very simple construction yet effective in use, and which may be connected in a circuit in various ways without any alteration of the construction.

Another object of the invention is to provide a device of this character which can be installed by .the ordinary user without requiring the services of an electrician, and so can be replaced at once so that service can be resumed whereas replacement of a lightning arrester usually puts the circuit out of commission until after replacement by a service man. Whatever may be the reason, it seems to be a fact that damage due to arcing through well-insulated parts or wiring has increased greatly in the part of the country served by the T. V. A., and especially so in rural sections.

Referring to the drawing, which is made a part of this application and in which similar reference characters indicate similar parts:

Fig. l is a plan of a housing having installed therein plug fuses and cartridge fuses, each type including specimens differing in construction from vone another,

Fig. 2, a section on line 2-2 of Fig. 1,

Fig. 3, a section on line 33 of Fig. 1, and

Fig. 4, a section on line 4-4 of Fig. 1, showing a connector detached from the fuse.

In the drawing reference character I indicates a housing or box having a lid II, here shown as pivotally connected to the body of the box. A horizontal partition I2 has a central opening in which are located sockets for fuses of different types. Electrical connections, etc., are provided underneath the partition, these latter forming no part of the invention. As part of the means for holding the fuses there are shown a plurality of sockets I3 in which plugs I4 and I5 may be located.

The plug I4, as shown in Fig. 3, comprises a central terminal I6 at the bottom, which is connected by means of a thin strip I8 forming a fuse link to a threaded terminal II encircling the plug. The top of the hollow casing of the plug is closed by a cap I9 which is bent inward about a shoulder on the plug to hold the cap permanently in place. At the center of the cap I have provided a member 2I, here shown as being in the form of a metal cylinder, either inunder the cap I9 and rests upon the top of the 5 plug.

The cylindrical member 2| preferably, but not necessarily, extends upward beyond the cap and in one method of use of my device a ground connection 23 is formed on the cap. This ground connection is here shown as being a U-shaped resilient piece of metal, one leg of the U-shaped member being secured to the lid II by a screw 24 and the other leg being arranged to contact with the upper end of the cylindrical member 2I when the lid is closed. The lower end of the cylindrical member 2I is spaced from the fuse link by a small piece of insulating material 25 resting on the flat face of the link and held in place by any suitable attaching means. The insulating material may be of any substance that will withstand a conventional voltage, e. g., a few hundred volts usually, it being of course proportioned to the Voltage and the size of the plug. A hinge 26 for the lid II is shown at the left of Fig. 3.

It will be seen that in ordinary use current may flow through the fusible link in ordinary manner, but upon occurrence of an emergency condition such as excess voltage due to a stroke of lightning or a surge due to other causes the insulation will be destroyed and the current will be passed off to ground, also destroying the fuse link and so preventing the excess current from passing into the domestic electrical appliances, or into whatever devices may be, protected by the safety fuse.

The plug I5 is similar in construction to the plug I4 but is shown as being connected to partition I2 as a ground, this connection being by means of a split plug 21 fitted into the member 2I as a socket, the plug 21 being carried by a suitable connector or pigtail 28 which is preferably flexible and which is secured to the partition I2 by means of a sleeve 29 and a screw 30. It will be seen that the shape of the part 2I renders it feasible to connect this member to ground either by means of a pigtail 28 or by means of a connection to the lid, which connection is interrupted when the box is open.

Fig. 2 shows in greater detail a pair of cartridge fuses 3|, 3| which are shown in section in said figure. These cartridge fuses are mounted on a removable bracket 32 by means of clamps 33 secured to said bracket, the bracket being entered in a pocket of a support 34 fixed to the box by screws 35, and carrying suitable electrical connections for causing current to flow through the clamps to the conducting heads of the fuses in the usual manner, such current passing from one head to the other through a flat fusible link 36 in each fuse. Each of the fuses is provided with an opening through the conventional insulating sleeve 3'! thereof and in each of these openings there is provided a cylinder 38 of conducting material such as copper. The inner end of the sleeve, which may or may not be closed, is spaced from the fusible link by a thin slip of insulating material of such a character that, like the slip 25, it may be instantly destroyed upon the occurrence of emergency conditions, such as excessive voltage in the circuit.

At the bottom of the pockets there is provided a resilient conductor, here shown as a leaf spring 40 held in place by a screw or rivet ll on a strap 42 of conducting material, here shown as grounded on the housing ID by the screw 35. At its ends the resilient member 40 is so shaped as to bear against the annular ends of the respective cylinders 38 and it will be seen that upon occurrence of excessive voltage or current the insulation 39 will be destroyed, permitting the current to escape to ground through cylinder 38 and connectors 40, 42 and 35, the fusible link being also destroyed at this time.

Instead of connecting the cartridge fuses to ground in the way indicated in Fig. 2 they may be connected to ground as shown in Figs. 1 and 4, where cartridge fuses 43, which may be identical in character with fuses 3|, are shown as connected to the ground through partition [2 by means of a sleeve 44 secured to the partition by screw 45, said sleeve forming one terminal of connectors or pigtails 46 and 41 which are preferably fiexible and each of which is provided at its other end with suitable connecting means such as a split connector 48 which is yieldable or slightly resilient and is shaped for entry into the cylinder 38 serving as a socket.

It will be obvious to those skilled in the art that many changes may be made in my device, all without departing from the spirit of the said invention; therefore I do not limit myself to what is shown in the drawing and described in the specification but only as required by the prior art.

Having thus fully described my invention, what I claim is:

1. In a device of the class described, a fuse casing, fuse terminals attached thereto, a fuse link within said casing and connected to said terminals, a metallic ground connection for said link mounted in and forming part of the wall of said casing, said ground connection having a terminal portion outwardly of the casing and extending inwardly of the .casing to a position closely adjacent said link, and a member of nonconducting material held between and in contact with said link and the inner end of the ground connection.

2. In a device of the class described, a plug fuse casing of insulating material, a center terminal at one end of said casing and a threaded shell terminal adjacent said end of the casing, a fuse link having a fiat portion connected to said terminals, a metallic ground connection mounted in the opposite end of the plug casing, said ground connection having an outer portion for connection to ground and a portion extending into said casing closely adjacent the fiat surface of said link, and a thin strip of insulating material held between said link and the inner portion of said ground connection.

3. A plug fuse as in claim 2, in combination with a housing having a movable lid, and a resilient ground terminal mounted on said lid in position to engage said outer part of the ground connection on the plug when the lid is closed.

4. In a device of the class described a cartridge fuse casing, fuse terminals attached thereto, a fiat fuse link within said casing and connected to said terminals, a metallic ground connection for said fuse comprising a member mounted in the wall of said casing and having an outer ground contact portion and a part extending into said casing closely adjacent a flat side of said link and a thin flat insulation strip held between said link and the inner end of said metallic ground connection.

5. A device as in claim 4, in combination with a housing and a flexible connector attached to the housing, said metallic ground connection being shaped to receive an end of said connector.

SPURGEON JONES. 

